1. Technical Field
The present invention relates to oscillator circuits, oscillator circuit groups, electronic apparatuses, and layout methods for an oscillation circuit group.
2. Related Art
When certain molecules adhere to the surface of a crystal oscillator that is in a resonance state, the resonance frequency changes according to the adsorption amount (weight). A technology using such a phenomenon is called QCM (Quarts Crystal Microbalance), and used in sensors for detecting the presence or the amount of molecules. As one of the applications of QCM, an odor sensor is known. The odor sensor is equipped with multiple oscillation circuits including oscillators having adsorption films formed thereon which selectively adsorb specified molecules.
For example, Japanese Laid-open Patent Application SHO 63-222248 (Patent Document 1) describes a technology that uses an element having a crystal oscillator with electrodes and adsorption films formed thereon (FIG. 6 in Patent Document 1) for detecting the presence of odor substance saturated in the air atmosphere by means of a change in the frequency.
Also, Japanese Examined Patent Application Publication HEI 08-012141 (Patent Document 2) and Japanese Laid-open Patent Application HEI 05-187986 (Patent Document 3) describe technologies for specifying the kinds of odors by using a plurality of crystal oscillators.
In order to make an odor sensor with high accuracy having an odor identifying capability equivalent to that of a human being or a dog, it is considered that several hundred odor sensor units each made of a combination of an oscillator, an oscillation circuit and adsorption films may be required. Therefore, in the case of an odor sensor having such a high accuracy, several hundred odor sensor units may preferably be arranged in an array configuration.
However, when numerous odor sensor units are arranged in an array configuration, input/output wirings of the oscillation circuits need to be densely arranged, and the wire-to-wire distance becomes smaller, which would cause a problem of crosstalk among closely arranged wirings. In particular, crosstalk poses a problem in equipments that operate at high frequencies. QCM sensors use high frequency signals on the order of MHz in order to increase the sensitivity of the sensors. Therefore, it is required to suppress such crosstalk of high frequency signals. In order to suppress crosstalk among wirings, it is possible to use a method of setting a greater wire-to-wire distance or a method to prevent mutual interference by using a shielded wire such as a coaxial cable or the like. However, either of the methods would result in a greater circuit area and a larger wire harness of cables, which entails a problem of higher manufacturing cost, and hindrance to size-reduction.